β-Adrenomimetic Actions in the Hypotension and Vasodilatation Induced by a Chromatographic Active Fraction from Bidens pilosa L. (Asteraceae) in Mammals

Bidens pilosa L. (Asteraceae) is routinely used in African pharmacopoeia for the management of inflammations, diarrhoea and cardiovascular disorders including hypertension. The implication of β-adrenomimetic agonist substances in the hypotension and vasodilatation induced by a chromatographic active fraction F2 of the leaves aqueous extract (BpF2) were investigated. BpF2 induced a dose-dependent hypotension (1 mg/kg b.w.- 25 mg/kg b.w.) in the rabbit. It caused a concentration dependent (10-12 mg/ml- 10-1 mg/ml) decrease in the force of contraction of the isolated guinea-pig aorta. The hypotension and vasodilatation elicited by BpF2 were attenuated in the presence of propranolol (a β-adrenoceptor antagonist). The results suggest that BpF2 could contain β-adrenomimetic agonist substances that may be partly responsible for the hypotension and the vasodilatation. This would therefore justify the use of the plant to treat hypertension.